i) Field of the Invention
This invention relates to water-in-oil type emulsified compositions, and more specifically to water-in-oil type emulsified compositions which are excellent in stability with time, form a highly water-repellant film on the skin, give users a pleasant feel upon use and are particularly suitable for use as cosmetic preparations or the like.
ii) Description of the Background Art
Emulsified compositions are classified roughly into an oil-in-water type (O/W type) and a water-in-oil type (W/O type). Of these, the water-in-oil type emulsified compositions have been used widely in skin care products owing to their excellent properties such that the affinity with the skin is good and the surface of the skin is hence covered with an oil film to prevent the transpiration of water, so that they avoid skin dryness and have a treating effect to the skin, and as base materials for cosmetic preparations such as makeup preparations or for medicaments because they are excellent in water repellency and keep makeup looking fresh, as compared with the oil-in-water type emulsified compositions.
These water-in-oil type emulsified compositions greatly affect the user's feel when applied to the skin because their oily bases form an external phase of an emulsion as a continuous phase. In order to give users a more pleasant feel upon use, various attempts have heretofore been made. For example, it has been practiced to change the oily base from hydrocarbon oil to ester oil, glyceride or silicone oil so as to reduce the oily feeling to the touch and to improve the conformability to the skin. In particular, it has been attempted to incorporate a large amount of a silicone oil as an oily base in water-in-oil type emulsified cosmetics because it provides cosmetic preparations which are dry and non-sticky to the touch, give users an agreeable feel upon use and have excellent water repellency.
However, when the silicone oil is used in a large amount as an oily base, a surfactant becomes hard to stably orient because of its poor compatibility with the surfactant, so that the surfactant tends to separate and cohere, and it hence is difficult to obtain a water-in-oil type emulsified composition good in stability. For this reason, various kinds of surfactants have been investigated with a view toward using them as an emulsifier. However, wholly satisfactory surfactants have not been found yet. For example, polyoxyalkylene-modified organopolysiloxane is known as an emulsifier used in usual water-in-oil type emulsified compositions. Even when this organopolysiloxane has been used in an emulsion containing a large amount of a silicone oil, it has however been difficult to obtain the emulsion with good stability. Besides, it has been attempted to thicken and gelatinize an oil phase in order to stabilize the emulsion state. However, thickening and gelling agents effective in the case where the silicone oil is contained in a large amount have scarecely been obtained.
As described above, any water-in-oil type emulsified compositions containing a large amount of a silicone oil and satisfying both feel upon use and emulsion stability have not been provided yet.